Public facilities must be tough to survive public use, the weather and cleaning. There are constant problems with switching devices which can be used in toilets, to activate automatic doors and carryout various switch requirements such as activating dispensers flushing, movement of toilet seats in a seat wash unit, sensor operated hand washing and drying in these facilities such as with toilets. Other public facilities include lifts, shower units, security devices, trains, buses, public buildings, lighting or any switching function in general.
Some switches being used are contact switches or contacts push buttons which include push button mechanisms incorporating a spring loaded button that when depressed will move a metal strip or conductor to contact between two electrical points providing a bridge that allows an electrical current to flow through from one point to the other. These switches are reliant on the contacts being clean to allow the current flow through but the contacts often corrode which can inhibit any low voltage electrical signal. Typically switches need to be self cleaning but with the low voltages being used, these switches can not self clean. Contact switches comprise plastic button heads which provide insulation to prevent any electrical shock but there have been problems with vandals who burn any switch cover to disable them. To meet disabled access codes any switch need to be a certain size which means that these switch tend to be industrial types having a housing construction that allows for easy unwanted removal by vandals.
Other switches being used are piezo pulse push switches but these required touching like the contact switches to operate. In a toilet situation, any touching can be a health concern for users whereby bacteria can be transferred. These switches consist of a bimetal disc that activates with a slight depression of a front disc surface when pushed causing contact with the surface behind providing a momentary pulse of electrical contact. They work well with electronic equipment that only requires a pulse of current to switch the relevant relay. These switches come in limited sizes of diameters up to 32 mm with a small LED or ring of light around the edge of the push button with a 16 mm switch. Piezo pulse switches have few moving parts and are more vandal resistant than contact switches but they still can easily be damaged by vandals by impact to cause them to either not work at all or work intermittently.
Other switches used, are microwave sensor switches which work by emitting and receiving microwaves on a continuous basis and detecting any change in the type of reflection received back. These come in a large box as they need to accommodate a cast dopler unit or electronic sensor plate. These types of switches are not suitable with metallic panels nor do their wide sensing range means they are not particularly suited to point switching.
Any light activated sensors or infrared sensors work by emitting and receiving back an infrared beam from the lens. These switches can come with a fixed range or an adjustable range that determines how far away from the face of the sensor it will sense an object. Within this range the beam is broken or obstructed to activate the switch. This switch is made from plastics and can include such features of a normal closed operation, normal open operation, PNP (switching with a positive output or NPN (switching with a negative output). Though users are very familiar with these types of switches and they can include many sizes with an activation light they suffer from several drawbacks. They are not very useful in this situation as vandals can easily deactivate these by covering with graffiti which may cause some users to be trapped within the toilet facility or they can burn the plastics of the switch. Their construction utilizes a double nut system like other switches which particular easy to dismantle from the front.
Appearance has to be considered in any switch as users may not see them to use them and various regulatory bodies have rules to allow adequate access and vision of any switch. As the switches are often required to be located externally of any facility they also need to be attractive in appearance.
In general capacitive sensor switches have a very short range and work by continually scanning the immediate environment. It activates when it senses a change in capacitance or density near the sensor head. Most capacitance switches recalibrate regularly to allow for any slow change in environment but will switch when a sudden change in capacitance is sensed. They are normally used in commercial applications such as manufacturing and comprise a large plastic case which is long in comparison to the sensor head. They have many disadvantages such as causing an adjacent metal surface to become an amplifying aerial so that touching the adjacent metal surface becomes the trigger for the switch. If water goes on the lens surface it will trigger the switch. The construction of these switches having long threaded barrels with two removable nuts, do not allow flush mounting thereby causing them to protrude and be less vandal resistant.
Commercially and practically there are long standing problems and needs in the industry to solve the problems of all the switches as discussed. There is nothing suitable to solve these problems, which necessitated the development of this invention.
In this specification unless the contrary is expressly stated, where a document, act or item of knowledge is referred to or discussed, this reference or discussion is not an admission that the document, act or item of knowledge or any combination thereof was at the priority date, publicly available, known to the public, part of common general knowledge; or known to be relevant to an attempt to solve any problem with which this specification is concerned.